I met this problem about twenty years ago. I gave up soldering instantly
and used PGA instead. Worked perfectly.

Inge



On 23 October 2013 15:03, Guy Ramsey <[log in to unmask]> wrote:

> Hi all,
>
> We would like to solder a thin gold foil, with some magic on top, to a PWB.
>
>
> The foil and pad are round, about 560 um in diameter.
>
> We want the solder connection to end up less than 25 um thick.  So, we are
> trying to print with a 50um thick stencil, and 20% reduction, the stencil
> aperture is 460 um diameter.  So, area ratio, or aspect ratio look great,
> printing shouldn't be a problem.
>
>
>
> Print results were inconsistent.
>
>
>
> This morning I realize that many of solder paste spheres are over half the
> thickness of the stencil.  And the rule of thumb that five spheres should
> fit across the aperture for good paste release.   Well, what about the
> thickness of the stencil versus the diameter of the spheres?
>
>
>
> Has anyone out there wrestled with this problem?  Maybe I should be using a
> thicker stencil, and push the aspect ratio a bit more.
>
>
>
> Thoughts?
>
>
>
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________